


How to care for your pregnant Merman

by Silverheartlugia2000



Category: Kingdom Hearts
Genre: Eggs, M/M, MerMay, Mpreg, Transformation, fish eggs, low descriptive sex in the first chapter, merman sora
Language: English
Status: In-Progress
Published: 2018-05-19
Updated: 2019-03-08
Packaged: 2019-05-09 01:06:04
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 4,017
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14706227
Author URL: https://archiveofourown.org/users/Silverheartlugia2000/pseuds/Silverheartlugia2000
Summary: Sora was just supposed to do routine Heartless duty in Atlantica, but a morning with Riku has him bringing home more than he expected.





	1. Fishy Fun

**Author's Note:**

  * For [MommaVanillaBear](https://archiveofourown.org/users/MommaVanillaBear/gifts).



**I’ve had such a block on updating lions pride and shadowed heart… I’m close to a full chap for each I just need to fill in a few gaps between scenes here and there! Anyway I’ve been aching to do more kingdom hearts and like I said still filling in the gaps, but I’ve been binging fan comics on YouTube all day which slipped towards the idea of MerMay and I thought, “ya know maybe I should give that one idea a crack?” I don’t know if I’ll finish it before May is over but it still counts if its started right??**

**Partially inspired by an author I faved a long long looooong time ago partially inspired by a conversation with mommavanillabear on ao3 a while back.**

**Basic idea I had was Sora coming back from Atlantica, but for some reason he’s stuck in his mer form still, and unable to access his normal form. Now I’m possibly leaning toward the cause being a bit um.. spicy so to say ;3**

 

 

 

Riku could be a real jerk at times. Sora loved him endlessly for sure, but when Riku KNEW he had a scheduled Heartless patrol in Atlantica in an hour and decided to use it as the perfect punishment for that prank he pulled last week when he repainted Riku’s favorite Komori Bat neon pink. It’s not like he couldn’t paint it back, which he did, but still!

 

Sora groans as Riku ploughs into him yet again. He was exhausted yet jittery, overstimulated yet still wanting. He had soft bites dotted along his back and chest bruises on his hips and he was sure if it wasn’t for the potions Riku was abusing to keep them both going he wouldn’t even be able to move right now.

 

As it was Sora’s hands were tied to the headboard panting and crying out hoarsely while his legs pulled Riku closer. The pace was hard and frantic now the gentleness of the first two rounds long gone as they were nearing the end of lucky number six.

 

On top of the lingering soreness that the potions didn’t completely erase Riku thought it’d be fun to plug him up in between. Letting his stomach swell and cramp with the build up each time, though the rubbing was oddly satisfying.

 

Riku seemed to like seeing him round and plump and full of Riku’s love. “I can almost imagine us having a little family.” He had told him once. They had talked about it before. Maybe in the future, when they were older and the Thirteen Darknesses were no longer looming threat, they could try looking into adopting or something.

 

Finally one last thrust and Riku cling tight to him, trembling with a growl. The new pressure added to his abdomen pushed Sora over as well his own voice little more than a worn squeak at this point. Riku falling limp on top of him, both breathless and utterly spent.

 

Once they managed to regain some composure Sora glances at the clock and whines. He was due to leave ten minutes ago and now in no way had time to clean up at all. Saying as much with the weak smack to Riku’s arm as the latter finally uncuffs him and kissed his poor wrists.

 

The Silverette only chuckles softly. “I can just portal you straight there if you’re that worried about it. Sure you don’t want to call sick now though?” Riku smiles slyly rubbing Sora’s belly again.

 

Sora shivers at the contact before wiggling away. He felt small barrier spell Riku had conjured in place of an actual butt plug activating again once his canal was free. Damn Riku had some very creative uses for magic..

 

“I can’t. The reports have been adding up and you’ve got to meet Mickey today. Kari’s at Radiant Garden and Axel is actually allergic to Atlantica. I didn’t know you can be allergic to a whole world but I guess fire powers don’t mix well with turning into a fish…”

 

Riku only smiles at Sora’s thoughtful frown. Hugging him close for one last soft kiss. “If you insist. But promise me if you aren’t up to it you’ll come back?”

 

“Aww come on I’ve gone out with worse than you being a little rough on me.”

 

_You’ve **done** worse to him. _ The nagging voice in Riku’s head piqued.

He pushed away the flashes of Sora’s betrayed face as the pirate ship fades away, the loss as the Kingdom Key pulls towards him, the disappointment at only being given a vague clue of where to go while the scratches and bruises from fighting a thousand Heartless weigh his tired body down.

 

“Sora..” said male droops at the soft spoken concern layered under a sternness.

 

Riku received a warm smile when the other turned to face him, a tan hand caressing his cheek while lips softly pressed against his. “I’ll always come back to you ‘Ku. Whether you want me to or not.”

 

Sora pecked him once more and rolled off the bed stretching out his sore muscles, Riku using one last potion just to be safe. “I’ve really got to get going now though. Guess I’ll take you up on that portal, the sooner I get there the less Heartless to make trouble for everyone.”

 

“It’s a good thing you don’t need clothes there then~” Riku chuckles, barely giving Sora time for an indignant squawk as he disappeared in a flash of light, the feeling of water surrounding him and stinging his eyes before his magic automatically kicked in.

 

Sora could feel his lungs squirm and shift, burning for breath a few seconds while slits opened up under his jaw and across his ribs the water flowing through with the ease of air. His modestly was quickly covered up with blue scales that tucked his bits neatly away in some fish equivalent. Legs melding together and spine twisting I what should be a painful way but was numbed by the same magic that changed him. As the scales crept down to his stretching feet and the dorsal fin extended from his rear Sora felt an unusual shift in his gut. He could tell the barrier spell was gone now that Riku didn’t need it anymore but his stomach churned oddly for a few minutes before settling.

 

Sora groans softly rubbing it. He still felt swollen but that should fix itself soon right? He wasn’t completely sure how his dolphin like half worked but he didn’t have problems relieving himself before. Maybe he’d just find a nice warm rock later to take a nap on after he killed off the Heartless. He heaved a sigh plotting a way to get Riku back while he swam off to start hunting.

 

——

 

His stomach never settles, not completely at least. The pressure didn’t so much release as rearrange and ease slightly. Once he was sure the Heartless had thinned out enough to not be a problem for a while. Sora made good on his decision on finding a nice mossy rock that was close enough to the surface he could be pleasantly warm.

 

He chances exploring his unfamiliar parts in an attempt to expel the trapped substance only ending up frustrated and needy again even after his fingers tried their hardest to get where the persistent throb echoed.

 

Giving into defeat and only slightly being able to satisfy himself Sora huffs laying on his stomach while his tail wrapped around the rock to anchor him in place for a nap. He still had a few hours before needed to be back anyway…

 

——

 

Hazy dreams faded and popped, the feeling of someone harshly shaking his shoulder caused him to jerk awake again.

 

“Sora!! Oh thank gods you’re awake!! Are you ok?! Did you get hurt?!”

 

“R’ku..?” Sora groans rubbing his eyes groggily, the blurry form coming into focus.

 

Riku was leaning, er- floating over him. The sun made his silver hair shine brightly, the scar Xemnas made visible on his shirtless side. Sora’s eyes trailed down examining the tiger shark tail with light silver scales and teal green stripes.

 

He was holding it awkwardly, like he didn’t know how to use it. Sora remembers that Riku had never even been to Atlantica yet, Sora wanted to wait till they could go together to teach him how to get around himself.

 

“Riku..? What are you doing here? How’d-“

 

“Sora you’ve been gone all night!!” The shark snaps interrupting him. His face set in an angry snarl and grabbing Sora’s shoulders, part to get his attention part cause the current was causing Riku to drift away. Huh he even had sharp teeth.. wait _what?!_

 

“ _What?!_ ” Snapping his eyes up to the surface didn’t show the hazy light of afternoon like he thought he would see but instead the budding light of dawn.

 

Looking back at Riku he saw the worry that lined his face, his eyes were tired and fingers dug into his skin a little more as the current shifted again.

 

Sora immediately let go of the rock to wrap around Riku instead. Tail twining around the others, Sora hugging Riku tight enough to squish his chest gills shut.

 

The shark clung back just as much if not more. Sora could feel the exhaustion waving off from him, some sense in his heart telling how Riku followed it for hours, struggling to get anywhere with a body he didn’t know but too panicked to waste time in figuring it out.

 

Riku didn’t show panic often. Mostly when he had dreams of deep booming voices and his body controlled by another mind. Sora has already been nearly lost to him twice. He wasn’t sure he could handle another. Sora in turn still had images of Riku’s back walking further away while he was trapped in place haunting him at times. But right now Riku was the one in need.

 

“M sorry Ku… guess I lost track of time. I’m ok though, I’m _fine_. Just dozed off was all.” Fingers petted through the short silver locks, the haircut might have been a good thing after all, he still didn’t know how Ariel and her sisters managed like they did.

 

Probably just the experience of growing up with it, but if Riku’s hair was still as long as it was and suddenly weight free in the water, he’d probably rip it out within minutes.

 

The thought made Sora’s lips twitch softly, but his stomach interrupts with a hungry growl. The dolphin cringes at the empty feeling, his tail gripping Riku tighter. It was then he noticed that the uncomfortable pressure from before was gone. But there was still a strange weight in his gut.

 

Riku huffed a short laugh, “You didn’t eat anything out here did you?” The only reply he got was a grumble and a heated face hiding against his collarbone. “Ready to go?” Feeling a nod the shark coaxed open a portal. Sora grumbling about the irony of giving swimming lessons to an island native as Riku slowly paddled them both through.

 

His legs were a bit wobbly coming out the other side but his grip on Sora never wavered. He expected the feeling of bare skin under his hands as Sora wasn’t wearing anything when he left. The smaller boy still clung to him as Riku stepped over to the bed where he had lain out Sora’s pajamas for when they got back.

 

It wasn’t until the grip around his middle tightened in panic, noticing Sora’s shaky breaths against his shirt, that worry pierced through his exhaustion, signaling something very _wrong_.

 

—-

 

He looked different than before. Master Sid had said it was just a slight Darwin effect that came with traveling worlds, as humans they didn’t change that much, but this..

 

Coming out of the portal Sora hadn’t changed back to his normal self. He was still a merman. And while in Atlantica he was perfectly able to spend time above water, here there seemed to be a time limit for it. His breath started to fail after a few panicked minutes of trying to force himself to change. Riku panicked racing off to Yin Sid who quickly conjured up a large tank upon seeing the boy.

 

Riku leaned against the glass now. Both of them tired, him from the long night and Sora from everything else that just happened.

 

The tail was longer, now flexible enough to wrap around Riku’s hips almost twice. The fin looked a bit less like a dolphin’s and closer to the tropical fish near their islands. Still strongly muscled so maybe a sports fish? The same color of blue but now with an added darker shade marbling over the back.

Sora’s fingers had neat claws, matching the small fangs probably meant to catch smaller prey with. His dorsal fin had stretched up his back as a short sail ridge that could be folded down flat. There were also new fins on his hips and arms to stabilize steering. Scales dotted his face and shoulders like freckles. His ears were a mix of elf like and fins.

 

But that all paled against the reason _why_ Sora’s magic won’t let him change back.

He still couldn’t believe this was his fault. Letting him get that full and trapping it there before sending him into a world that changes your very being to adapt to it.

It somehow triggered a strange reaction in the transformation and now Sora was trying to develop _eggs!!! Merman eggs!!_

Master Sid hadn’t had a hard time worming it out of them after examining Sora. They were teens after all and Sora was horrible at hiding embarrassment. Riku’s spunk was trapped long enough in the transition between forms that Sora’s magic warped his normal body change to handle it in a way that fitted Atlantica. And the overnight stay had given it time to set.

 

And it was only the first stage of it still! The “fertilization” alone was apparently enough to convince Sora’s body that changing forms now was dangerous both to himself and the barely started eggs. He was trapped like this until they were ready..

 

Right now Sora lay on the bottom with his back to him. Riku wasn’t sure if he was sulking or just trying to process still. The Fairies had thought enough to add a few things to Sora’s new temporary home at least. The tank had been moved up to their room, both getting enlarged quite a bit to be reasonably roomy. He had a bed of sorts tucked in one corner that was turned into a covered alcove. Like the hollow rocks people put in fish tanks for hidey holes. Soft and malleable like a beanbag with a few weighted blankets, big enough for him, his tail and then some. Complete with a movable screen for privacy. The rest of the floor covered with a variety of stones and a few plants. The water would filter and oxygenate itself but they would need to research a diet. For now it was deemed safe for Riku to give him a plate of raw tuna flank that he surprisingly wolfed down without a second thought before settling into his current stew.

 

All in all it was a pretty cozy place Riku supposed, for a fish anyway. But in the end was still just that. Sora was reduced to being a pet on display, trapped in a cage, unable to leave whenever he wanted and pretty much helpless if he even tried.

 

Sora never took well to getting cooped up. The week he got chickenpox his poor mom lost count on how many escape attempts were made.

 

He said he would always come back to Riku. But would this be enough to tear them apart in the end?

 

**For those who are curious on what I mean on the Darwin effect. I’m taking the evolutionary theory as an excuse to mess with Sora’s looks and instincts. When he landed in Atlantica his form was crafted to the Disney laws of The Little Mermaid. Now that he’s not in Atlantica anymore. He’s closer to what a mer would be like from Destiny islands, his home world. Thing is though, DI dosen’t have mers so Sora is in a sense a new species which in consequence is closer to natural instinct than an Atlantican would be. And as a new species Riku doesn’t have a guide of what to expect, leaving him shit outa luck~ :3**


	2. Chapter 2

**Jez… almost a full year to finally update this… I couldn’t get the right feel to this for the longest time. I’ve got an outline of how I want this to go at least, probably not long but hopefully its something!**

 

Sora didn’t know what to feel anymore. After a full two hours of ignoring him Sora finally gave into Riku’s attempts to talk to him from the top of the tank. He reached up and grabbed the older boy by the shirt pulling him into the water. Sora clung tight to his boyfriend, his tail unconsciously wrapping around Riku’s waist to hold him closer as Sora cried into his chest. Luckily there was the alcove nearby so Riku could sit on top of the rock and not get pulled under, he sat rocking and cooing to Sora to what felt like ages.

 

He was afraid of what would happen to him as time went on, worried about the other worlds and his friends while the team was a Keybearer short, confused on just HOW this particular change was triggered as it’d never happened any of the other times Sora had a mission after romping with Riku, and also frustrated cause apparently the magic that changed his form wasn’t the only thing on the fritz as both his Keyblade and his spells refused to work when Riku suggested practice exercises to keep his mind off things. The only thing he conjured was sparks of thunder that enveloped his body protectively and somehow managing to make the artificial current in the tank change directions slightly. (just why does Sora have water magic in 3 all of a sudden? ;3 )

 

 

But what bothered Sora most right now, is that something in his mind felt satisfaction. He had the perfect shelter, there weren’t any larger predators around he was given plenty of food and sleepy, he felt _safe_. _Safe_ because Riku was nearby, near enough to watch over him, to care for him, to protect him. _Safe_ with his _mate_ to _provide_ for him while he was _vulnerable_ and _nesting_.

Sora was scared and angry and confused, but he also felt _safe_.

 

 

The feeling was not the same a week later.

 

He couldn’t help but get more and more irritable, the tank itself was the perfect shelter yes but it wasn’t enough, it was too small too still, his muscles felt both cramped and full of energy, he was bored out of his mind, the food Riku brought him had dulled in his mouth, it wasn’t fresh enough to still have the warmth of life, it wasn’t as satisfying as catching it himself would be.

 

Something about the bed was bothering him too, there was an idea of instinct in his head on how to make it into proper nest, yet it wasn’t good enough no matter how many times he tried, nothing made it feel good enough and he didn’t have the right materials at all.

 

Worst of all was his hormones, he needed Riku, craved Riku in the worst way both intimately and for comfort with all the fears in his head and after waking from muddy dreams with a familiar, dreadful cackle ringing in his ears, but he just found something wrong with him every time they got close. Sora had always liked the way Riku looked but Sora’s instincts found him off putting now for some reason. What was left of his wavering patience reasoned out that maybe it was just how separated they were like this, Sora couldn’t come out of the water and Riku couldn’t stay in for very long…

 

\-----

 

Sora had gotten to a point where he couldn’t even use real words anymore. Any time Riku tried to talk to him he’d get clicks and trills in response. Any time he tried to join Sora in the water the brunet seemed both overly clingy but stand offish at the same time, pushing him away with flared fins. Riku knew Sora wanted something from him, but with these new behaviors and lack of actual communicating he was at a loss.

 

Riku had asked Yin Sid about it but the wizard was still gathering information on what he could. Destiny Islands had no native merfolk, as such they had to piece together things from what they knew about mers from varying worlds as well as any natural fish that looked anything remotely like Sora.

 

The best they can figure is that Sora was forced into some form of protandry, in which his reproductive fish genes have switched from male to female, even if overall he is still male, and theoretically was Riku’s sole dominance over him that _might_ have triggered the change. But it didn’t explain just _why_ it hasn’t happened _before_. Especially since any species they found to compare to Sora were incapable of such.

 

His behavior however was a total guess, while they did see signs that he was trying to fill his bed with things he never seemed satisfied with it, he picked up things from around the tank and arranged them then emptied it all out again with a screech and start over. His fins seemed to respond to his emotions too, flaring up to make himself bigger when he was especially angry, or lying flat when Sora curled into himself after waking from nightmares. More often than not Riku ended up spending most the night sitting on the alcove roof holding Sora just so he could sleep.

 

The only other thing Riku could clearly read off him was the worsening claustrophobia of being in the same room for so long.

 

Finally, one day Riku had been talking to Yin Sid in his office about their options when they both heard a sharp crack along with a rush of water. Riku rushed back, only to see His Sky draped out on the floor, a hole in the upper part of the tank and the water pouring out at a steady pace.

 

As Yin Sid hastily repaired the damage Riku gathered up the flailing merman in his arms, lack of oxygen had Sora twitching uncontrollably in instinctual panic. With a powerful leap Riku lifted them both over the lip of the glass and back into the water holding himself afloat while supporting the smaller. It took only three breaths for Sora’s head to clear and that was all he needed to start writhing, screeching terribly with something close to tears in his eyes. Pent up emotion and energy had started leaking into his magic causing thunder sparks to shoot out into the water, Riku hissed in pain gripping Sora tighter, his heart aching at the pain his light was in. There was blood in the water from where Sora had rammed into the glass.

 

They needed help, they needed answers, Riku didn’t even pause to think it through as his Keyblade tore a portal through space.

 

**Biologist nerd in me finds it interesting that fish can change genders in addition to the frogs mentioned in Jurassic Park along with a few others, wiki it if you want more info~ https://en.wikipedia.org/wiki/Sequential_hermaphroditism and yes I know it says fems are the bigger ones but we will ignore that bit, I like Sora small :3 As for his magic only using thunder (with a hint of water): fire isnt great against water, blizzard is probably hazardous to tropical fish, I’m ignoring other elements, and no Keyblade is just for plot X3 plus I think itd be neat if thunder manifested into an electric eel esque defense mechanism?**


End file.
